Pocket for immobilizing inert gas in battery cathodes



Filed Dec. 5, 1948 D 2, 952 F. T. BQWDWCH 2,6 11

POCKET FOR IMMOBILIZING INERT GAS IN BATTERY CATHODES 2 SHEETS-SHEET 1 'Dec. 2, 1952 F. T. BOWDITCH 2,620,371

POCKET FOR IMMOBILIZING INERT GAS IN BATTERY CATHODES Filed D60. 3, 1948 2 SHEETS-SHEET 2 ENTOR INV FREDERICK T. BOWDITCH U %ORNEY Patented Dec. 2, 1252 POCKET 'FORIMMOBILIZING INERT GAS IN BATTERY CATHODES Lakewood, Ohio; assignor,

Frederick T. Bowditch,

by mesne assignmen ts, to Union Carbide and Carbon Corporation, a corporation of New York Application December 3, 1948, Serial No. 63,276

6 Claims.-

7 1 This inventionrelates to an improvedgas activated dry cell of the type disclosed in the copending application Cahoon et al. Serial No. 52,988, filed October 6, 1948, for Primary Galvanic Cell and Battery and Methodof Making Same, in which the possibility of non-uniform electro chemical action on the anode by the electrolyte has been minimized. An object is to reduce the possibility of loss ofcapacity incident to the creation of inert gas pockets in the diffuser blocking the passage of the depolarizing gas to the central portions of the cathode on activation in an evacuated container. It is impractical to make this evacuation prior to activation so complete that no inert gas remains, either in the residual atmosphere or adsorbed on the cell surfaces. It has been discovered that such inert gas can be flushed ahead of the depolarizing gas on activation; and contained in a small cathode space if that space is empty.

Referring to the drawing:

Fig. 1 shows a shallow mold in which thediffuser portion is formed;

Fig. 2- shows the diffuser and mold after a longitudinal slot has been formed in the diffuser; Fig. 3 is a section on the line 3-3 of Fig. I.

Fig. 4' shows a battery of two cells in an enclosed casing.

A shallow mold Won a support 9 is laid over a coated zinc anode and filled with a plastic mixture II of granular carbon with a suitable binder, the latter being adapted for baking out to form a porous diffuser'in cemented relation to the anode I8 of a cell of the above mentioned type of which the present invention is an improvement. An appropriate smoothing blade I2 is adapted to smooth over the top of the material II and the mold II) forming a diffuser body of uniform depth. In the embodiment illustrated the smoothing blade I2 is fixed in a movable support so that relative movement between the mold and smoothing blade forms the diffuser material to a uniform depth of about .07 inch. After being suitably smoothed and formed, a plate I3 is placed over the top of the diffuser material resting against an end and edge of the mold so that the slot I5 in the plate I3 is centrally located over the material II. Handles I4 for the plate have been found to assist in lowering and orienting the plate I3 into position on the mold. After the plate I3 has been placed over the mold a shouldered tool not shown is moved along the slot with the nose of the tool projecting through the slot I5 for cutting the slot I6 in the diffuser material II. A shoulder on the tool cooperates with the top surface of the plate and prevents the tool cutting below' the material into the zinc anode I8 and its con ductive coating Il. After the slot Iii has beencut the plate I3 is removed by lifting the plate with the aid of the handles: I4. The zinc anode I3 and diffuser assembly are then removed from the mold. and subjected to a baking operation, which acts to set the binder, and so provide a firm, adherent diffuser member, as described. in the co-pending application of Zimmerman and Cahoon Serial No. 53,174, filed October '7, 194%.

now Patent 2,572,296, for Primary Celland Battery and Methodof Making Same.

In Fig. 4 is shown a battery of two'cel'ls embodying this invention enclosed within a=casing I9. Each cell is thinner than has been shown; but is magnified in breadth in order to illustrate the two cathode portions, one of which is a wet mix cake 2B in which the depolarizing gas goes into solution, and the other is a porous conductive diffuser member II, through which thedepolarizing gas is supplied from all four of its edges or sides. Such pipe 22 when the valve 23"has been opened. Before the admission of chlorine through the pipe 22, any residual inert gas ispreferably firstsucked out through the pipe 24 controlled by valve 25. An immobilized electrolyte H is contiguous the anode I8, and the entirebattery is under some pressure axially thereof.

Before this invention it was found that following activation by the admission of chlorine tothe cell container, a dead space existed in the center of the cathode where the chlorine did not penetrate on account of the presence of inert gases imprisoned there by the in-rushing chlorine. By cutting a groove of the type illustrated, only in the diffuser, chlorine gas is enabled to approach the wet mix cake and enter into aqueous solution from all directions, up to the edges of the slot I6, any inert gas being driven ahead of the chlorine into the slot, where it immobilizes the smallest possible cathode surface area. In practice it was found with a cathode 10'' x 18" in area that the slot I6 functioned satisfactorily when made about 8 long and about wide or less. With these dimensions the slot I6 has an area of 2 square inches and the cathode portion has an area of square inches. Thus the slot has an area which is 1.1 of that of the cathode difiuser portion II. From the drawing it may be seen that this slot is located substantially equidistantly from the edges of the diffuser portion. As shown in Fig. 3 the gas enters through the 3 depth of the slot is preferably the full thickness of diffuser (the purpose being to concentrate the required storage space for inert gas over the smallest possible cell area).

The cell of this invention is preferably stored in an atmosphere of an inert gas such as nitrogen. Before being activated the main body of the inert gas is drawn from the battery casing by a vacuum pump. However, a residual layer is thought to remain at least as a molecular layer adsorbed on the various surfaces, particularly the porous diffuser. The in-rushing depolarizing gas will sweep the portions of inert gas ahead of it by physical action and also by reason of the fact that the chlorine will preferentially wet the surfaces on which the inert gas may be adsorbed. The difference in boiling points of the inert and of the depolarizing gas, chlorine, is believed to be responsible for this preferential adsorption.

What is claimed is:

1. In thin flat deferred action type of gas depolarized cell provided with an enclosing casing, a, supply pipe for depolarizing gas for said casing, valve means in said pipe controlling the supply of depolarizing gas to said cell, said cell having a cathode in two parts, one of which is a wet mix cake in which the depolarizing gas goes into aqueous solution and the other cathode part is a porous carbonaceous conductive diffuser member through which the depolarizing gas is adapted to be supplied to a contiguous face of the wet mix cake, the edges of the diffuser member being spaced from the casing to enable depolarizing gas to enter said diifuser member from its edges, the combination therewith of the improvement for more completely removing the inert gas from said diffuser part of the cathode than would be the case if evacuation were relied on, said improvement comprising said diffuser being provided with a central recess spaced approximately equidistantly from its edges and of a size occupying but a small minor portion of the area of the cathode, whereby depolarizing gas entering the diffuser portion through its edges will be capable of sweeping any adsorbed portions of inert gas in the diffuser into said recess on activation of the cell, said recess being closed in a direction normal to the plane of the cell by adjacent cell elements.

2. A cell according to claim 1 in which the r cess is of substantially the depth of the diffuser thickness and of an area of about 1.11% of that of the diffuser.

i 3. A cell according to claim 1 which has a recess which is rectangular in cross section and said recess is elongated and is many times longer than it is wide.

1. In the method of activating a deferred action gas depolarized dr cell having a cathode comprised of a thin fiat Wet mix cake in which the depolarizing gas goes into aqueous solution and a thin fiat porous carbonaceous diifuser portion through which the depolarizing gas enters its edge portions for distribution to most of the area of the wet mix cake when said cell has been stored in an atmosphere of inert gas, the combination therewith of the improvement for obtaining substantially complete removal of inert gas from the diffuser portion of the anode, said improvement comprising evacuating inert gas from in and around said cell and then flowing depolarizing gas into the said diffuser portion through opposite edge portions, and substantial- 1y simultaneously sweeping portions of inert gas from opposite directions within the diffuser into a central recess in the diffuser.

5. A method according to claim 4 in which the incoming depolarizing gas releases adsorbed portions of the inert gas by the preferential wetting afiinity the depolarizing gas possesses for the carbonaceous diffuser material compared to that of the inert gas.

6. A method according to claim 4 in which the inert gas is nitrogen and the depolarizing gas is chlorine.

FREDERICK T. BOWDITCH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 356,261 Pearce Jan. 18, 1887 357,646 Upward et al. Feb. 15, 1887 668,215 Reed Feb. 19, 1901 1,011,559 Benko Dec. 12, 1911 1,060,468 Little Apr. 29, 1913 1,607,759 Keller Nov. 23, 1926 1,765,673 Huntley June 24, 1930 2,154,312 MacCallum Apr. 11, 1939 FOREIGN PATENTS Number Country Date 7,189 Great Britain May 28, 1886 14,050 Great Britain June 13, 1911 208,196 Germany Jan. 26, 1908 

1. IN THIN FLAT DEFERRED ACTION TYPE OF GAS DEPOLARIZED CELL PROVIDED WITH AN ENCLOSING CASING, A SUPPLY PIPE FOR DEPOLARIZING GAS FOR SAID CASING, VALVE MEANS IN SAID PIPE CONTROLLING THE SUPPLY OF DEPOLARIZING GAS TO SAID CELL, SAID CELL HAVING A CATHODE IN TWO PARTS, ONE OF WHICH IS A WET MIX CAKE IN WHICH THE DEPOLARIZING GAS GOES INTO AQUEOUS SOLUTION AND THE OTHER CATHODE PART IS A POROUS CARBONACEOUS CONDUCTIVE DIFFUSER MEANS THROUGH WHICH THE DEPOLARIZING GAS IS ADATED TO BE SUPPLIED TO A CONTIGUOUS FACE OF THE WET MIX CAKE, THE EDGES OF THE DIFFUSER MEMBER BEING SPACED FROM THE CASING TO ENABLE DEPOLARIZING GAS TO ENTER SAID DIFFUSER MEMBER FROM ITS EDGES, THE COMBINATION THEREWITH OF THE IMPROVEMENT FOR MORE COMPLETELY REMOVING THE INERT GAS FROM SAID DIFFUSER PART OF THE CATHODE THAN WOULD BE THE CASE IF EVACUATION WERE RELIED ON, SAID IMPROVEMENT COMPRISING SAID DIFFUSER BEING PROVIDED WITH A CENTRAL RECESS SPACED APPROXIMATELY EQUIDISTANTLY FROM ITS EDGES AND OF A SIZE OCCUPYING BUT A SMALL MINOR PORTION OF THE AREA OF THE CATHODE, WHEREBY DEPOLARIZING GAS ENTERING THE DIFFUSER PORTION THROUGH ITS EDGES WILL BE CAPABLE OF SWEEPING ANY ADSORBED PORTIONS OF INERT GAS IN THE DIFFUSER INTO SAID RECESS ON ACTIVATION OF THE CELL, SAID RECESS BEIN CLOSED IN A DIRECTION NORMAL TO THE PLANE OF THE CELL BY ADJACENT CELL ELEMENTS. 